Many of us won't have heard of underwater welding, but it's actually a very important thing in many industries. Underwater welding includes a lot of different processes that join steel on offshore oil platforms, pipelines, ships, and in many other applications.
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| Underwater Welding |
It can be done at regular or at high pressures, and can be done in a wet environment or a dry one. Let's take a look at some of the benefits and downsides of different kinds of welding underwater, and the uses of this interesting technique.
Dry welding is the most useful method for making any weld in very deep water, or in cases where the weld needs to be extremely strong. On many sea structures and vessels, strength is extremely important.
The problem is that most conventional dry welding techniques are very expensive, and takes a very long time. While some other techniques, using a smaller hyperbaric chamber for just the area of the weld, are being developed, they're not the standard yet. As they become more popular, wet welding may fall out of use entirely.
That's because wet welding, while much cheaper and faster, just isn't all that strong. It tends to create pockets of oxygen and hydrogen gas, as well. These occur due to the electrolysis of water, and can be dangerous and even potentially explosive!
In addition, the majority of wet underwater welds won't last long. They're a temporary fix that needs replacement after only a little while. These welds are best used when time and money are short, and function needs to be maintained - they'll need to be redone again later using a dry process.
It's important to remember that there are some limitations on how deep you can weld, as well. Dry welding can be done as deep as eighty meters below the surface of the water, but it requires special diving equipment. Wet welding is much less effective under high pressure, since the join isn't really strong enough to stand up to the forces additional depth will put on it.
When tested to destruction, a dry weld can achieve more than twenty percent elongation of the weld. Wet welding is rated for up to seventeen percent, but usually fails at a little more than half that. For deep water repairs, it's just not the best choice.
Even among dry welding methods, there are some that work better than others. One common dry underwater welding method is to use a hyperbaric chamber. This is expensive and time consuming, but completely encloses the worker and the site of the weld, though it does retain some risk of hydrogen absorption into the weld itself.
Cofferdam repairs are also useful. However, this kind of dry weld doesn't remove moisture or humidity from the area of the repair. That means that hydrogen absorption is a risk in this kind of weld, unless heated inert gas is used to fill the area around the weld.
Last, and less common, but growing in popularity, is the NEPSYS type of system. This is a less expensive method of dry welding in high pressure situations, and takes less time to construct than other methods. It also uses a technique that removes the danger of hydrogen absorption, making it a safer way to repair all kinds of underwater structures and vessels.
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